State Capitol Building, Room 216 

P.O. Box 720 

Jefferson City, Missouri 65102 

Dear Governor Nixon: 

Thank you for your staffs recommendations dated September 25, 2015, on air quality designations for 

the state of Missouri for the 2010 revision to the primary National Ambient Air Quality Standard for 

sulfur dioxide. Reducing levels of sulfur dioxide pollution is an important part of the U.S. 

Environmental Protection Agency's commitment to a clean, healthy environment. Exposure to sulfur 

dioxide can cause a range of adverse health effects, including narrowing of the airways which can cause 

difficulty breathing and increased asthma symptoms. This letter is to notify you of our preliminary 

intentions regarding your staffs recommended designations. 

On June 3, 2010, the EPA strengthened the health-based or primary standard for sulfur dioxide by 

establishing a standard for one-hour average sulfur dioxide concentrations at a level of75 parts per 

billion. Within one year after a new or revised standard is established, the Clean Air Act requires the 

governor of each state to submit to the EPA a list of all areas in the state, with recommendations for 

whether each area meets the standard. Through an interactive process, the EPA considers the 

recommendations and then promulgates designations for all areas across the country. On July 25, 2013, 

the EPA designated 29 areas in 16 states as nonattainment, but did not at that time designate other areas. 

Pursuant to a March 2, 2015, court-ordered schedule, 1 the EPA must complete the remaining sulfur 

dioxide designations by three specific deadlines: July 2, 2016, December 31 , 2017, and 

December 31, 2020. 

This current round of designations, to be completed by July 2, 2016, addresses two groups of areas: ( 1) 

areas that have newly monitored violations of the 2010 sulfur dioxide standard based on the most recent 

three calendar years of certified monitored ambient air quality data, and (2) areas that contain any 

stationary source that had not been announced as of March 2, 2015, for retirement and that according to 

the EPA's Air Markets Database emitted in 2012 either (i) more than 16,000 tons of sulfur dioxide or 

(ii) more than 2,600 tons of sulfur dioxide with an annual average emission rate of at least 0.45 pounds 

of sulfur dioxide per one million British Thermal Units. 

1 Sierra Club v. McCarthy, No. 3-13-cv-3953 (SI) (N.D. Cal. Mar. 2, 2015). 

*Printed on Recycled Paper 
Intended Unclassifiable/ Attaimnent 

Area 

Scott County 

Intended Unclassifiable/ Attainment 

Area County 

Scott County 

The asterisk (*) indicates the designation or boundary for this intended nonattainment area represents a 

modification to the designation or boundary that you have recommended. 

Because, at this time, the EPA does not have conclusive information to determine whether the following 

areas are meeting or not meeting the sulfur dioxide standard, the EPA intends to designate these areas as 

unclassifiable: 

Intended Unclassifiable Area 

Jackson County* 

Intended Unclassifiable County 

Jackson County (p) 

(p) indicates portion of county 

The asterisk (*) indicates the designation for this intended unclassifiable area represents a modification 

to the designation that you have recommended. 

Based on ambient air quality data collected between 2012 and 2014 indicating a violation of the 2010 

S02 NAAQS, the EPA initially identified an area in Missouri as one that would potentially create the 

obligation for us to designate by July 2, 2016. The consent decree directs the EPA to evaluate data 

collected for the most recent three years (i.e., between 2013 and 2015), and Missouri has submitted to 

the EPA complete, quality assured and certified data for calendar year 2015 for Iron County indicating 

compliance with the 2010 S02 NAAQS. As a result, the EPA intends to designate this area by either 

December 31, 2017, or December 31, 2020. 

The enclosed teclmical support document provides a detailed analysis that supports our intended 

designation decisions. If your state has additional information that we should consider prior to finalizing 

these designations, please submit it to us by Apri119, 2016. We also will be publishing a notice in the 

Federal Register announcing a 30-day period for the public to provide input on our intended designation 

decisions. We will promulgate the designations for these areas by July 2, 2016. We will designate all 

other previously undesignated areas in the state on a schedule consistent with the prescribed timing of 

the court order, i.e., by December 31, 2017, or December 31, 2020. 
Mark Hague 

Enclosure 

cc: Sarah Parker Pauley, Missouri Department of Natural Resources 

Kyra L. Moore, Missouri Department ofNatural Resources 

Janet G. McCabe, USEPA Headquarters 

Stephen D. Page, Research Triangle Park